#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
	double x1, x2, x3, y1, y2, y3,a,b,c,p,s;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	a= sqrt((y1 - y2) * (y1 - y2) +(x1 - x2) * (x1 - x2));
	b=sqrt((y1 - y3) * (y1 - y3) + (x1 - x3) * (x1 - x3));
	c= sqrt((y3 - y2) * (y3 - y2) + (x3 - x2) * (x3 - x2));
	p = (a + b + c)/2;
	s = sqrt(p * (p - a) * (p - b) * (p - c));
	printf("%.2lf", s);
	return 0;
	
	




}